The present invention relates to card punches, and relates more particularly to an improved structure of card punch which has a rectangular hole punching unit and a circular hole punching mechanism respectively operated by the same operating handle for punching rectangular holes or circular holes on paper.
Various card punches have been developed for punching holes on loose leaves, and have appeared on the market. FIGS. 6 and 7 show a rectangular hole card punch according to the prior art. This structure of card punch comprises a base 40, a punching and binding unit 41 raised from the base 40, a plurality of rectangular punching elements 42 driven by an operating handle 44 through a transmission mechanism (not shown) to punch paper, and a plurality of pull rods 43 respectively connected to the rectangular punching elements 42. By means of the pull rods 43, the rectangular punching elements 42 can be selectively moved out of the respective operating position so that the operating handle will not be able to drive the respective punch element(s) that are in the inoperative position. The punching and binding unit 41 further comprises a row of projecting rods 45, and a row of actuating rods 46 moved by the operating handle 44 relative to the projecting rods 45 for binding punched sheets of paper on the flat teeth 48 of a loose-leaf clip 47 (see FIG. 8). When the operating handle 44 is turned in one direction, the actuating rods 46 are moved forwards from the projecting rods 45 to open the loose-leaf clip 47 for permitting punched loose leaves to be loaded on the flat teeth 48 of the loose-leaf clip 47. When the operating handle 44 is turned in the reversed direction, the actuating rods 46 are moved backwards to the projecting rods 45 to close the loose-leaf clip 47, and therefore the punched loose leaves are fastened to the loose-leaf clip 47.
The aforesaid rectangular hole card punch is functional. However, this structure of rectangular hole card punch is applicable only for punching rectangular holes on paper. Loose leaves with rectangular binding holes cannot be firmly retained together by a loose-leaf clip with circular teeth. Therefore, when a loose-leaf clip with circular is used to fasten sheets of paper together, these sheets of paper must be punched by a card punch with circular punching elements. Regular card punches with circular punching keys are not adjustable. For punching different numbers of binding holes on paper, different card punches with different numbers of circular punching elements have to be separately used.